A light emitting diode (LED) refers to a device that emits light through recombination of carriers (electrons or holes) in a p-n junction structure of semiconductors and can realize a variety of colors using various compound semiconductors such as GaAs, AlGaAs, GaN, InGaN, AlGaInP, and the like.
Such light emitting diodes are operated at lower power and have longer lifespan than typical light bulbs or fluorescent lamps, can be installed in a narrow space, and are invulnerable to vibration. In addition, the light emitting diodes are used in a display device and a backlight unit and have expanded their application to general lighting apparatus, large LCD-TV backlight units, automobile headlights, and general luminaires due to good characteristics thereof in terms of reduction in power consumption and durability.
However, in order to achieve application of light emitting diodes to various fields, typical light emitting diodes are required to have improved luminous efficacy, to solve a problem of heat dissipation, and to achieve high brightness and high output. Recently, in order to address such problems, semiconductor light emitting diodes have attracted increasing attention.